1. Field of the Invention
The present invention relates to a printer, copier, facsimile apparatus or similar image forming apparatus and more particularly to an image forming apparatus capable of managing the limit of use of a process cartridge or similar replaceable part thereof to thereby promote sure maintenance, and a replaceable part and an IC (Integrated Circuit) chip for the same.
2. Description of the Background Art
In an electrophotographic image forming apparatus, a photoconductive element, toner and so forth joining in an image forming process each are usable only for a preselected period due to wear and other causes. Such parts have customarily been constructed into replaceable process cartridges to be replaced by the user.
It is a common practice to manage the time for replacing a process cartridge to thereby allow the cartridge to be replaced before it approaches the limit of use and effects, e.g., image quality. The management may be based on the number of prints from which the amount of use of the process cartridge can be estimated. In light of this, the number of prints output with a process cartridge is counted in order to store the cumulative number of prints in a memory, which is built in the cartridge. When the cumulative number of prints reaches a limit number of prints assigned to the process cartridge, a time for replacing the cartridge is reported.
The memory of the process cartridge has customarily stored various kinds of management data including not only the cumulative number of prints and limit number of prints but also. ID information particular to the cartridge. The memory therefore needs a great capacity. On the other hand, the apparatus body processes all of such data, i.e., identifies the process cartridge, determines the cumulative number of prints, and determines whether or not the cumulative number of prints has reached the limit number of prints. Data should therefore be transferred from the process cartridge to the apparatus body each time of processing, slowing down the overall processing.
Generally, the limit number of use assigned to the process cartridge is fixed without regard to the sheet size, image ratio and other image forming conditions, which are dependent on the user. It follows that a toner cartridge, for example, storing much toner and therefore bulky and expensive is necessary for a user whose deals with images having an extremely high image ratio. Conversely, as for a user dealing with images having a low image ratio, such a toner cartridge would reach the limit number of use with much toner left therein.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 10-49031, 10-52964 and 10-198236.